Petitioner, Tom A. Mitchell (Mitchell) filed a claim against respondents, Ideal Cement and its insurance carrier, the State Insurance Fund (hereafter collectively Ideal) for work-related injury to his lungs and upper respiratory system purportedly caused by 13 years continuous exposure to various forms of dust and fumes in the workplace. At trial Mitchell introduced the deposition, with attached medical report, of Dr. G.C., who opined Mitchell has an impairment of 25% to the body as a whole secondary to a class 2 respiratory impairment and damage to his lungs as a result of his employment with Ideal. In his deposition he indicated Mitchell suffered from emphysema and bronchitis. In addition to other defenses not pertinent here Ideal alleged both that Mitchell suffered from no impairment and, in any event, no injury was caused by the workplace environment. The former defense was presented by the medical report of Dr. J.A.; the latter primarily through testimony of an industrial hygienist, lay witnesses employed at the plant and safety studies at Ideal’s plant and other cement plants. Over various objections the trial court admitted both parties’ medical evidence and Ideal’s evidence concerning causation. In his order the trial court ruled in pertinent part, “[] claimant has failed to establish on the weight of the evidence that he sustained occupational disease (personal injury) arising out of and in the course of employment”.

The Court of Appeals, in a 2-1 decision, reversed and remanded to the trial court for entry of an award of 25% permanent partial disability on the basis the only medical evidence having probative value was that of Dr. G.C. It determined the report of Dr. J.A. had no probative value. The Court of Appeals did not directly reach any issue concerning causation or consider the non-medical evidence on this subject, even though review of the record below reveals it was a primary issue and determined adversely to Mitchell by the trial court.

In our view, even if one were to exclude consideration of the report of Dr. J.A., as the Court of Appeals did, the trial court’s decision must be affirmed because the other evidence presented by Ideal on causation is more than sufficient to support the decision of the trial court that Mitchell suffered from no injury caused by the work environment.1 As to the causation issue there can be no question on this *1046record the decision of the trial court is supported by competent evidence. Only in the absence of competent evidence may a trial court’s decision be viewed as erroneous and subject to reversal. Parks v. Norman Municipal Hospital, 684 P.2d 548, 552 (Okla. 1984).

Recently, we determined an employer does not have to present medical evidence to refute causation. Collins v. Halliburton, 804 P.2d 440 (Okla. 1990).2 Collins also involved a claim of lung and upper respiratory disease purportedly caused by the workplace environment. In Collins we upheld a decision of the trial court denying benefits, which was based on testimony of an industrial hygienist who offered an expert opinion that the facility involved was safe for workers and medical records that the claimant there had been an asthmatic for many years. We find Collins controlling here.

Ideal’s evidence as to causation included testimony of an industrial hygienist, who conducted air quality tests at Ideal, that generally the various types of dust and fumes at the facility and their levels would not cause harmful effects to the workers there. He also testified the consistent wearing of a protective mask would reduce the level of dust to a negligible amount. Other evidence was presented concerning making the wearing of masks mandatory in certain areas in the mid-70s. Testimony was also presented from petitioner himself concerning his mask-wearing history which generally showed he consistently wore his mask in high dust areas of the plant. There was also evidence that Mitchell smoked a half a pack of cigarettes a day for 15 or 20 years and that he still smoked at the time of trial, although he testified not as much.

In workers’ compensation cases it is not our responsibility to weigh conflicting proof, but to review the record to determine whether a trial court’s decision is supported by competent evidence. Parks v. Norman Municipal Hospital, supra, at 552. Although the evidence is not one-sided on the causation issue, the record does contain competent evidence supporting the decision of the trial court. In such a situation there is no basis for reversing the decision of the trial court.

Accordingly, the decision of the Court of Appeals is VACATED and the order of the Workers’ Compensation Court is SUSTAINED.